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1 of 10 www.rohm.com JAN. 2013 - Rev.A© 2013 ROHM Co., Ltd. All rights reserved.
Switching Regulator Series
BD9528AMUV PCB Layout that Uses Only 1ch
This application note illustrates example of PCB layouts when only 1-ch is being used, for the 2-ch buck DC/DC controller IC
BD9528AMUV. It also explains the pin-connections for the unused functions and the PCB layout guidelines. All characteristics
have to be verified separately, and not guaranteed by the PCB layout shown here.
Setting Conditions
1. Electric characteristics:
VIN = 24V, VO1 = 3.3V, IO = 4A max, OCP = 6.0A、Switching frequency = 320kHz, VREG1 = 5V, VREG2 = 3.3V.
2. PCB specification:
Two-layers FR4, Minimum line width 0.15mm, Minimum gap 0.15mm, Minimum hole-diameter 0.3mm.
3. External switching transistor(s):
- In example-1 of PCB layout, use dual type N-ch MOSFET SH8K15 for the switching transistor.
- In example-2 of PCB layout, use dual type N-ch MOSFET RQ3E150GN and RQ3E180GN for the switching transistor.
Circuit Diagram
CONTROL MODE MCTL1 MCTL2
PWM fixed mode High High Low
SLLM mode (Light-load pulse skip)
Low Low
QLLM mode (Silent pulse skip)
Low High
No.13027EAY06
Figure 1. Circuit diagram
VIN
CTL
EN1
EN2
REG1
REG2
REF
SS1
FS1
BOOT1
HG1
SW1
LG1
PGND1
FB1
BOOT2
HG2
SW2
LG2
PGND2
VIN
C1
CTL
EN1
REG1 5V C2
C4
C5
Q2
Q1C7
VIN
C30 C9
30
9
21
4
29
28
12
19
6
15
22
23
24
26
25
14
3
2
1
31
32
BD9528AMUV
L1
R17
VO1 C14 C13
FS2 10
MCTL
AGND
FB2
PGOOD1
PGOOD2
PGOOD1
18
13
MCTL1
11
20
5
SS2
Vo1
Vo2
ILIM2 8
ILIM1 17
27
7
R5
R7
R18
MCTL2 MCTL16
Open
Open
Open
REG2 3.3V C3
Application Note
2 of 10 www.rohm.com JAN. 2013 - Rev.A© 2013 ROHM Co., Ltd. All rights reserved.
BD9528AMUV PCB Layout that Uses Only 1ch
U1 IC - Buck DC/DC Converter BD9528AMUV ROHM VQFN032V5050
C1, C9 Ceramic Capacitor 10µF50V, X5R, ±10%35V, X5R, ±10%
GRM55DR61H106KA88GRM32ER6YA106KA12
MURATA57503225
C2, C13 Ceramic Capacitor 10µF 10V, X5R, ±10% GRM31CR61A106KA01 MURATA 3216
C3 Ceramic Capacitor 10µF 6.3V, X7R, ±10% GRM21BR70J106KE76 MURATA 2012
C4 Ceramic Capacitor 0.1µF 10V, X5R, ±10% GRM155R61A104KA01 MURATA 1005
C5 Ceramic Capacitor 2200pF 25V, X5R, ±10% GRM155R61E222KA07 MURATA 1005
C7 Ceramic Capacitor 0.47µF 10V, X5R, ±10% GRM188R61A474KA61 MURATA 1608
C14 POSCAP 220µF 6.3V, ±20%, ESR 25mΩmax 6TPE220MAP SANYO 7343
C30 Ceramic Capacitor 0.1µF 50V, X7R, ±10% GRM188R71H104KA93 MURATA 1608
L1 Inductor 6.8µH ±30%, 5.2A(L=-30%), DCR=27.6mΩ max 1217AS-H-6R8N (DEM8045C) TOKO 8080
Q1 MOSFET - N-ch, Vdss 30V, Id 15A, Ron 4.7mΩ RQ3E150GN ROHM 3333
Q2 MOSFET - N-ch, Vdss 30V, Id 18A, Ron 3.3mΩ RQ3E180GN ROHM 3333
R5, R7 Resistor 75kΩ 1/16W, 50V, 5% MCR01MZPJ753 ROHM 1005
R17 Resistor 56kΩ 1/16W, 50V, 1% MCR01MZPF5602 ROHM 1005
R18 Resistor 15kΩ 1/16W, 50V, 1% MCR01MZPF1502 ROHM 1005
ReferenceDesignator
ManufacturerPart Number
ManufacturerConfiguration
(mm)Type Value Description
Bill of Materials
Application Note
3 of 10 www.rohm.com JAN. 2013 - Rev.A© 2013 ROHM Co., Ltd. All rights reserved.
BD9528AMUV PCB Layout that Uses Only 1ch
Example-1 of PCB Layout ・Dual type N-ch MOSFET SH8K15 is used for switching transistors Q1 and Q2.
・MCTL1 and MCTL2 pins are connected to the Low-Level, and set to SLLM (light-load pulse skip) mode.
Figure 2. Example-1 of PCB Layout Top Layer + Bottom Layer (Top View)
Application Note
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BD9528AMUV PCB Layout that Uses Only 1ch
Example-1 of PCB Layout (Continuation)
Figure 3. Example-1 of PCB Layout Top Layer (Top View)
Application Note
5 of 10 www.rohm.com JAN. 2013 - Rev.A© 2013 ROHM Co., Ltd. All rights reserved.
BD9528AMUV PCB Layout that Uses Only 1ch
Example-1 of PCB Layout (Continuation)
Figure 4. Example-1 of PCB Layout Bottom Layer (Top View)
Application Note
6 of 10 www.rohm.com JAN. 2013 - Rev.A© 2013 ROHM Co., Ltd. All rights reserved.
BD9528AMUV PCB Layout that Uses Only 1ch
Example-2 of PCB Layout ・Dual type N-ch MOSFET RQ3E150GN and RQ3E180GN are used for switching transistors Q1 and Q2.
・MCTL1 and MCTL2 pins are connected to the Low-Level, and set to SLLM (light-load pulse skip) mode.
Figure 5. Example-2 of PCB Layout Top Layer + Bottom Layer (Top View)
Application Note
7 of 10 www.rohm.com JAN. 2013 - Rev.A© 2013 ROHM Co., Ltd. All rights reserved.
BD9528AMUV PCB Layout that Uses Only 1ch
Example-2 of PCB Layout (Continuation)
Figure 6. Example-2 of PCB Layout Top Layer (Top View)
Application Note
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BD9528AMUV PCB Layout that Uses Only 1ch
Example-2 of PCB Layout (Continuation)
Figure 7. Example-2 of PCB Layout Bottom Layer (Top View)
Application Note
9 of 10 www.rohm.com JAN. 2013 - Rev.A© 2013 ROHM Co., Ltd. All rights reserved.
BD9528AMUV PCB Layout that Uses Only 1ch
Notes for PCB Layout
1. Arrange input decoupling capacitor C30 on the same side as the switching transistors Q1 and Q2, and place it as near as
possible to the power supply and the ground terminal of the switching transistor(s). Try to shorten this distance even by 1mm. The
switching noise increases when input decoupling capacitor C30 is far away, or if arranged by the via-hole on the reverse side.
There is no problem when the decoupling capacitor C30 for high frequency is near the switching transistor(s), and even if the input
bulk capacitor C9 is somewhat away.
2. In order to minimize the radiation noise by the inductor L1 from the switching node, arrange it near to switching transistor(s)
Q1 and Q2, although it is not a requirement for input capacitor C30. Do not widen the copper pattern area more than it is needed.
3. Arrange output capacitors C13 and C14 near to inductor L1, and their ground to be separated from the ground of input
capacitors C9 and C30. A lot of high-frequency switching noises are included in the ground of the input capacitor, which can be
propagated to the output ground if they are near.
4. Wire the ground of switching transistor Q2 to the terminal pins PGND1 and PGND2 of the IC. Make sure not to cause the
potential difference between the two, due to voltage drop caused by the wiring.
5. Wire the ground of output capacitor C14 to the terminal pin AGND of the IC. Minimum influence by switching noise is made by
wiring to a clean ground.
Figure 8. Notes for PCB layout
1
2
3
3
4
5
7
8
Application Note
10 of 10 www.rohm.com JAN. 2013 - Rev.A© 2013 ROHM Co., Ltd. All rights reserved.
BD9528AMUV PCB Layout that Uses Only 1ch
6. Wiring for the feedback path to IC is taken from the load side, and not to arrange it from output capacitor C14 side or in
parallel with the noise source of switching transistors Q1, Q2 and the inductor L1.
7. Connect the decoupling capacitor C1 to the VIN terminal of IC and is placed near to the IC terminal pin, and ground to PGND.
8. Connect the decoupling capacitors C2 and C3 to the VREG1 and VREG2 of the IC, and is placed near to the IC terminal pin,
and ground to AGND.
Figure 9. Notes for PCB layout (Continuation)
6
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Examples of application circuits, circuit constants and any other information contained herein are provided only to illustrate the standard usage and operations of the Products. The peripheral conditions must be taken into account when designing circuits for mass production.
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